Everyone is talking about EVs and HEVs, but Stop-Start vehicles provide a good interim means to save fuel and reduce emissions. We at CAP-XX agree that Stop-Start vehicles – with potentially more than 100 starts per day – could quickly kill a standard lead-acid battery in less than 18 months. Supercapacitors can support vehicle batteries by supplying the peak current (300A plus) for each engine start, enabling longer battery life. Check our site for tests we ran on batteries supported by supercapacitors vs batteries alone: Slides 3 – 9: http://www.cap-xx.com/resources/docs/CAP-XX%20-%20Supercapacitors%20for%20Automotive%20Applications%20%28website%29.pdf

It's not such a futuristic concept, though. You can separate out the H2 from a hydrocarbon fuel, like gasoline or E85 or whatever, on board. And then you feed that H2 to a fuel cell on board, and the electricity to electric motors.
You can do an online search and see that people are working on just this sort of scheme.
Since fuel cells have a hatd time with generating high current bursts of energy, a hybrid-sized battery is probably needed too.

Indeed, we will have crossed a major threshold when EVs can generate their required electricity on board.
What we need is Dr. Emmett Brown's futuristic DeLorean that was powered by a "Mr. Fusion" reactor that ran on banana peels and other organic matter :)

And I'm always curious about where all of these EV gurus and enthusiast like JB Straubel think and believe the electrical power is coming from and how it is generated. Blue sky or all of it solar and wind? I doubt. More fossil fuel (coal, natural gas and oil) fired power generating plants will be needed to support the demand. How about addressing the efficiency/energy loss from the energy generating source all the way to the 'plug'?

Really? Look back 10 years, 20 years, 50 years...the reserves of fossil fuels keep getting bigger as we discover new reserves and the "known" reserves keep expanding even though we are consuming more. Natural gas has expanded into known reserves of hundreds of years with the discovery of shale gas...with the mild winter in the US, there is talk of near term negative pricing (that's right... suppliers paying some customer to TAKE gas) in the WSJ. Seems unlikely, but the bottom line is that fossil fuel energy is not running out in our lifetimes nor is it going to be priced away...the invisible hand has a way of finding new reserves when the pricing mechanism pushes it.
Take a look at the inflation adjusted price of electricity in the US over the last 50 years...it has hardly budged from a small band. It is not in an inexorable state of growth by any measure, unless you live in CA where the legally forced mix of renewable energy is causing pricing to rise artificially. Drop the regs and the prices will drop rapidly.
We aren't going to dramatically change the way we live, and move to happy 800 sq ft apartments next to our workplace. Guess what? They do that already in China. It's called Foxconn, and I'm sure their workers are efficient consumers of energy, but it doesn't sound like it's all unicorns and rainbows in that world. I prefer my big house in the suburb and am ok with my commute, as are most Americans.
Gasoline has recently gotten expensive because of speculation about the Iran political situation, and because we have turned down building a pipeline to the massive reserves in Canada. The supply of oil is vast, and gets bigger as the price per barrel goes up. It's not running out in our lifetime.

As we continue to deplete the supply of fossils fuels they will become ever more expensive. Few of us will even be able to afford the gas for a 100 mpg fossil fuel vehicle. Certainly in the next 20-30 years we will experience this. We will dramatically change our transportation requirements - live closer to work, live in smaller self contained communities etc. Between now and then EVs will become a major part of our transportation infrastructure. I believe we see a combination of incremental improvements along with some quantum leaps forward in energy storage systems. I won't call them batteries because they won't resemble anything like the battery we have today.

Moore's law is predicated on having the processing techniques being the limiting factor rather than the materials properties being the limiting factor. Batteries have been at the materials limit for a while. Making a significant breakthrough in battery capacity and cycle life would required developing new materials. This would be akin to developing a new class of semiconductors.

I agree with Bert. Batteries blow, and will always blow for any realistic solution to replace gas. Synthetic fuel converted from natural gas with a fisher-tropsch type process, or generated from renewables in a similar fashion could use the existing infrastructure and offer something closer to the energy density we're accustomed to.

I still don't think battery (Li-ion or any kind) be a good solution to power up EV. Even with 30min fast charge time is still too long for recharging and I bet it more or less hurt the battery run time (life) with today's battery chemistry. I hope some day we can have better energy storage technology to really boost the performance. Of course, some gentlemen above mentioned that at the end the energy has to be self-generated onboard. Wind, Solar or ??? I just don't know what will happen but surely something great must happen before we can claim cars to be free from fossil fuel.

Based on battery manufacturer's claims, EVs are on the cusp of being economically viable in NA compared to conventionial vehicles.
In Europe, with $7 per gallon gas, they are economically viable on paper.